“This is worse than I thought it would be,” our contractor said as he stood in our half-finished shower. “This is embarrassing.”

My husband and I were having our upstairs bathroom—a black-and-white bath original to our 1951 Arlington Colonial—gutted and updated. We’d been happy with how prompt and neat the crew had been for its week at our house, but three days into the tile work, we contacted the owner of the firm: A number of our travertine tiles didn’t line up, and some were badly cut. We wanted him to see the sloppy work and have it fixed.

“This tile all has to come down,” the contractor finally said. “I’ll get my best stone guys on this project.”

He did. And he paid for new tile.

My husband and I had learned our first lesson in bathroom renovation: All tile setters are not the same. The workman who had laid our stone wasn’t a novice—he had, according to the contractor, recently done an intricate ceramic-tile backsplash. But he’d never installed stone, and natural stone—which is uneven and heavy—is hard to work with. Tile setters usually charge $2 to $5 per square foot more for stone.

Lesson one: Make sure the person laying your tile has experience with that material—especially stone and glass. Most experts at laying stone can usually lay ceramic or porcelain, which is easier. It doesn’t always work the other way.

Tales of renovations gone wrong are frequent cocktail-party banter. What you often hear is that renovation takes longer and costs more than the contractor tells you. Both were true: Our project, which the contractor had estimated would take four weeks, took 20 weeks and cost 5 percent more. At least the crew finished the work—we’d been warned about contractors who take the money and run.

While our contractor made mistakes, so did we. Here are nine other things I learned the hard way about bathroom renovation.

Even if you’re just giving a bathroom a facelift and not changing walls or plumbing, it pays to consult a designer.

Our first mistake was assuming that because we were just ripping out old tile and fixtures and putting in new—sometimes called a facelift—we didn’t need a bathroom designer.

We were redoing two bathrooms—the black-and-white one on the second floor and a 30-year-old bath with ocean-blue fixtures in a first-floor addition. We had flipped through books and magazines and found photos of the looks we wanted. We had interviewed three contractors and one design/build firm, showing them our photos and getting estimates.

The upper range of the design/build firm’s quote was twice what the three contractors wanted to do our 5½-by-6½-foot upstairs bathroom. (The design/build firm would give us only a range, not a firm estimate, until we paid a $500 design fee.)

My husband was impressed by the design/build firm’s reputation and leaned toward going that route. I balked at spending so much more on a “simple” project. To this day, my wonderful husband has never blamed me for the challenges we had.

We assumed we could get design advice from our tile shop and our contractor. After all, they did bathrooms all the time. The contractor we chose says his firm does at least 40 bathrooms a year.

A few tile shops we visited offered suggestions—some have staff designers, and you can make an appointment. But many tile shops, including the one where we bought our travertine, are staffed by salespeople who know the products but who aren’t designers.

Contractors aren’t designers, either. We threw the contractor a curve when, before signing on the dotted line, we decided to replace the upstairs tub with a luxurious shower. Now it wasn’t a simple facelift. We should have hired a designer at that point.

One reason our first tile setter had problems is that no one had drawn the space for him and figured out where to start the tile and at what height. As he came to the window and had to make the tile in the shower line up with the tile outside the shower, he ran into problems.

Before the owner of the contracting company had the mislaid tile taken down, he brought in a designer to measure the room and to decide exactly where to place the tile, including where accent pieces would go. The new crew followed his drawing and had no problems.

In hindsight, the extra money the design/build firm wanted may have more than paid for our time and frustration. We spent many Saturdays shopping for tile, fixtures, and accessories. While we still would’ve had to do some of that with a design/build firm, it would have handled more details and narrowed our choices. It also would probably have saved us from ordering the wrong tub for our downstairs bath. More on that later.

“One misconception a lot of people have is that bathrooms are easy,” says Mark Richardson, president of Case Design/Remodeling. “Bathrooms, from a design-and-construction point of view, are the hardest.”

It’s worth asking if a design/build firm has a certified bathroom designer on staff; not all do. A friend who paid a design fee to one firm was sent shopping for tile and fixtures with a woman she assumed was a designer but who turned out to be the office bookkeeper.

Lesson two: Unless you know design, it’s worth hiring a bathroom designer. Even if you don’t want to pay for a designer or a design/build firm to work on a project from start to finish, some independent designers offer advice for a flat fee—say, $250. At the very least, make sure your contractor has thought through or sketched out your bathroom, especially tile placement.

You usually get what you pay for.

That’s a golden rule you hear all the time, whether buying shoes or furniture. Still, homeowners often assume that a remodeler wanting twice the price for a project is marking up labor and materials too much. That’s sometimes true, but good subcontractors with more experience charge higher hourly rates. Bathrooms require experienced craftsmen—we learned that when our contractor brought in the second tile crew.

“A good question to ask is ‘How many of this type of project did you do in the past 12 months?’ ” says Richardson. “Ninety-nine percent of remodelers are generalists, not bathroom specialists. They may have done only four bathrooms in the past year.”

There’s no guarantee that a high-priced plumber or tile setter will do the job perfectly. Still, says Dee David, a bathroom designer in Falls Church, “you can’t get good quality at a cheap price. If you’re working with Joe in the truck, he probably won’t be able to deliver on your expectations.”

Our contractor gave us a one-year warranty on the work; the pricier design/build firm, we later learned, offers five years. In this economic climate, it’s also a good question whether a contractor will be in business next year—the more established the company, probably the better the chance.

Besides, says Mike Weaver of W.T. Weaver & Sons, a plumbing showroom in Georgetown, “people are always trying to save money, but they’ll probably not redo their bathroom for a very long time, so it’s important to do it right.”

You’ll have to take time off work to visit showrooms and meet contractors.

In an area where many people work long hours and some Home Depots are open around the clock, my husband and I assumed that bath showrooms would have evening and weekend hours. We were wrong.

Some tile and plumbing-supply shops are open Saturdays; a few are open Sundays or after hours by appointment. But many are geared to contractors, opening at perhaps 7 am and closing at 3 pm, with no weekend hours.

“If you want a good-quality designer, a good-quality contractor, you need to work with them on their schedule,” says David.

Lesson four: Be flexible. Contractors can’t always work around you—and you may not want to hire those who can.

Small baths are harder to renovate.

Partway through our project, a bathroom designer told me that small bathrooms are harder for contractors.

We’d had our own problems designing our small upstairs bath. We had to find a sink no wider than 20 inches—harder than it sounds—and a fairly compact toilet. We went to several showrooms before finding what we wanted at Union Hardware in Vienna.

What we didn’t know is that small spaces are hard for contractors, too. They’ve got to fit a lot into a small space, and there will be more frequent tile cuts.

A bigger issue, says Dee David, is that smaller bathrooms are often in older homes. A home more than 40 years old has settled, and the walls and floor may no longer be level or square. A contractor can adjust for that. In our case, the company installed new subfloor and laid the floor tile on a diagonal to hide the slightly off-square walls. But you may not know what you’re dealing with—for example, hidden water damage or plumbing problems—until the plaster and drywall come down.

“From both a design and technical standpoint,” says Case’s Richardson, “bathrooms are the riskiest renovations. There’s plumbing, there’s electrical. If you do something wrong, the cost and pain of fixing it are great.”

Lesson five: If you have an older home, be prepared for surprises.

A bathroom may be the smallest room in a house, but there are dozens of decisions.

We had spent hours at a tile shop picking porcelain and ceramic tile for the walls and floor of our downstairs bath. Then the saleswoman said, “Now you have to pick your grout.”

I groaned. Already there had been more decisions than we’d expected for both bathrooms: What style of trap did we want under the wall-mounted sink upstairs? What seat did we want on our dual-flush Toto toilet? Did we want the edges of the bullnose tile round or straight?

“In the past few years there have been more new choices in bathroom products than in all of the past 100 years,” Richardson says. “It’s overwhelming.”

It wasn’t that we didn’t have answers for most of questions; it’s that after a while the level of detail became mind-numbing—so much so that we made mistakes.

When ordering the tub for downstairs, I was presented with two cast-iron choices by Kohler that would match my sink. The saleswoman suggested that the tubs were similar except in price—one was $600 more. I couldn’t see the cheaper tub in person; it wasn’t on display. Because she seemed to be suggesting there was no reason to pay extra, I chose the less expensive model. I never took a hard look at the dimensions. Only later, when the tub was delivered, did we realize it was a builder-grade model too shallow and narrow to allow a decent bath. Waiting for the new, more comfortable tub held up the project two weeks.

It wasn’t the only mistake we made on materials. When the downstairs bath’s floor tile was incorrectly installed—laid straight instead of diagonally—the contractor offered to redo it. At the tile shop, I opted for a different tile that was in stock rather than waiting two weeks for the original tile to come in. But I didn’t realize that the pattern of each ceramic tile would vary greatly from the sample—until the tile was on the floor. Next time, I’d look at every tile in the box and take out the ones I didn’t like.

It’s important to think through every detail. “A typical thing people don’t think about when planning their bathroom is accessories,” says Dee David. “I tell people that planning where the towel bar is going is just as important as the height of the sink.” Or you may finish the bathroom and realize you didn’t leave space for a towel bar.

Another common problem, says Sarah Bernheisel of Renaissance Tile & Bath in Alexandria: “People plan for the fixtures but don’t think enough about storage.”

Lesson six: Take snacks with you on your shopping excursions; they may take longer than you expect.

Bathrooms cost more than you’d think.

“What surprises my clients is how labor-intensive bathrooms are: They’re the most expensive rooms to renovate per square foot,” says Dee David. “That’s because it can take 20-plus people to create a bathroom—the designer, the person you picked the tile from, the guy who cuts the mirror, the guy who does the light.”

Lesson seven: Although a bathroom is a small space, you may have many strangers in and out of your house, from the plumber to the tile setter to the painter.

Don’t dwell just on design—consider function.

Before my husband and I embarked on our project, we gave a lot of thought to what we liked and didn’t about our bathrooms. It’s one reason we tore out the tub upstairs—we never used it. We also installed extra lighting in both dark bathrooms.

In my bath, I weighed a jetted tub versus non-jetted, a shower door versus a curtain. I changed the mirror placement so it was easier for me to get ready in the morning.

But I admit that I gave more thought overall to looks than to function. I had fallen in love with a particular Kohler pedestal sink, and I had the bathroom built around it. I spent hours poring over the sink faucet and the tile but only minutes picking a showerhead and the heated floor—decisions that later mattered when the showerhead was too low and had to be raised and the heated floor didn’t work as well as I thought it would.

“There’s a natural tendency on the part of homeowners to immediately go to a showroom and choose product instead of taking an inventory of their needs,” says Case’s Mark Richardson.

My husband and I had also debated whether to gut both baths or simply do cosmetic touchups. Why not tile over the chipped floor and refinish the tub? One contractor pushed us in that direction—but the price wasn’t that big a savings.

Valery Tessier-Leon, a project designer at Case Design/Remodeling, says that when clients ask her that—“Should I just tile over?”—she counters with “How long do you plan to stay in your home?” If a bathroom is more than 20 years old—a typical lifespan, she says—and you expect to be in the house another decade or more, you might save money by gutting a bathroom in which problems, such as a cracked shower pan, could surface later.

Lesson eight: Before you go shopping, think about how you use your bathroom, what you’d change, and how long you plan to be in your house.

Your contractor will make decisions you may not like or understand.

Anyone who has had renovation done knows that you may come home at some point, look at the work that’s been done that day, and think, “Why did they do that?”

We had a number of those moments, as with a light fixture that wasn’t centered over the medicine cabinet, an oddly cut windowsill, and a shower seat much larger than we’d discussed. Some things were done for a reason; others were not but weren’t worth changing. For example, we had told our contractor three times to use ivory grout on the stone tile. We came home to sand-colored grout—which I ended up liking better.

We talked to or e-mailed our contractor almost every day and met with him weekly, trying to avoid surprises. For the most part, our contractor had no problem when we asked to have something fixed.

Lesson nine: If a contractor does something you don’t like, point it out. But if you’re a perfectionist, you’ll need to let go of some things or you’ll go mad. No one but you is going to notice sand-colored versus ivory grout.

Try to keep the project in perspective.

For many people, bathrooms are a sanctuary—and if they’re spending all this money on renovating their sanctuary, they want to sweat the details and get it right.

Like many a homeowner who has done renovation, I became obsessed with it. I’m sure I drove my contractor crazy. It was sometimes all I could talk about with friends, family, and colleagues—sorry about that, guys—because it was front and center in my mind. It’s stressful: When you come home to chaos and dust and strange men with power tools, your home is no longer a haven. The Friday we came home to the poorly laid tile, I barely slept.

A few days after that sleepless night, I got an e-mail from a friend about someone we knew who had been diagnosed with cancer. It put our bathroom in perspective.

My husband and I planned more date nights to get out of the house, with its drop cloths. Fun evenings helped diffuse some of the stress.

Despite all the aggravation, we’re happy we did our bathrooms over. “Having said everything I said about the risks in redoing a bathroom,” Richardson says, “a bathroom is one of the most important investments you can make in a house.”

Lesson ten: When your bathroom is done, it may not be perfect. I could point out things in our beautiful new baths that I’d now do differently. But I’ll let them go. After all, each looks so much nicer than it did. And it’s just a bathroom.